Combustion in a diesel engine is lean combustion in which the ratio of oxygen to fuel is high, which causes an increase in the amount of NOx (nitrogen compound) in exhaust gas emission. However, recent diesel engines achieve satisfactory emission performance in a steady region.
As a technique relating to the invention, there is known a technique for enhancing followability of air-fuel ratio control and reducing exhaust gas emission.
[Patent Document 1] Japanese Laid-open Patent Publication No. 2000-110574
However, it is important to improve engine performance not only in a steady region but in a transition region where acceleration or the like is performed.
The invention has been made to solve the above problem, and an object thereof is to provide an intake system control device and an intake system control method capable of improving engine performance in a transition region.